HTML <! Doctype> Label

HTML in <! What is the role of the doctype> tag? <! The doctype> declaration is positioned at the front of the document, before the

Definition and Usage:

<! The doctype> declaration must be the first line in the HTML document, before the

<! The doctype> declaration is not an HTML tag; it is a directive that instructs the Web browser to write which HTML version of the page to use.

In HTML 4.01, <! The doctype> declaration references a DTD because HTML 4.01 is based on SGML. The DTD prescribes the rules of the markup language so that the browser renders the content correctly.

HTML5 is not based on SGML, so you do not need to reference a DTD.

Label For example:

<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 strict//en" "HTTP://WWW.W3.ORG/TR/XHTML1/DTD/XHTML1-STRICT.DTD" >

In the above declaration, the root element of the document is declared HTML, which is defined in the DTD that the public identifier is defined as "-//w3c//dtd XHTML1.0 strict//en". The browser will understand how to find a DTD that matches this public identifier. If it is not found, the browser uses the URL following the public identifier as the location for the DTD.

Resources

The difference between HTML 4.01 and HTML5

There are three types of <! in HTML 4.01 Doctype> statement. There is only one of the HTML5:

<! DOCTYPE html>

Common DOCTYPE declarations

HTML 5

<! DOCTYPE html>

HTML 4.01 Strict

The DTD contains all the HTML elements and attributes, but does not include the display and deprecated elements (such as font). Frameset (framesets) is not allowed.

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01//en" "HTTP://WWW.W3.ORG/TR/HTML4/STRICT.DTD" >

HTML 4.01 Transitional

The DTD contains all the HTML elements and attributes, including both display and deprecated elements (such as font). Frameset (framesets) is not allowed.

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >

HTML 4.01 Frameset

The DTD is equivalent to the HTML 4.01 transitional, but allows the frameset content.

<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 frameset//en" "HTTP://WWW.W3.ORG/TR/HTML4/FRAMESET.DTD" >

XHTML 1.0 Strict

The DTD contains all the HTML elements and attributes, but does not include the display and deprecated elements (such as font). Frameset (framesets) is not allowed. tags must be written in well-formed XML.

<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 strict//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" >

XHTML 1.0 Transitional

The DTD contains all the HTML elements and attributes, including both display and deprecated elements (such as font). Frameset (framesets) is not allowed. tags must be written in well-formed XML.

<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 transitional//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">

XHTML 1.0 Frameset

The DTD is equivalent to XHTML 1.0 transitional, but allows frameset content.

<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 frameset//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd" >

XHTML 1.1

The DTD is equivalent to XHTML 1.0 Strict, but allows models to be added (for example, to provide Ruby support for East Asian languages).

<! DOCTYPE HTML PUBLIC "-//w3c//dtd XHTML 1.1//en" "Http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd" >

HTML <! Doctype> Label